1. Field of the Invention
The present invention relates to a compressor suitable for an air conditioner in a vehicle or the like.
This application is based on Patent Application No. Hei 9-329661 filed in Japan, the contents of which are incorporated herein by reference.
2. Description of the Related Art
FIGS. 3-5 show an example of a conventional scroll-type compressor. FIG. 3 is a sectional view in the longitudinal direction, FIG. 4 is a sectional view along line "F--F" in FIG. 3, and FIG. 5 is a sectional view along line "G--G" in FIG. 4.
In FIG. 3, reference numeral 1 indicates a closed housing which comprises cup-like main body 2, front end plate 4 fastened to the body 2 using bolt 3, and cylindrical member 6 fastened to the front end plate 4 using bolt 5.
Main shaft 7 is provided through cylindrical member 6, and is supported in a freely rotatable form via bearings 8 and 9.
In the closed housing 1, fixed scroll 10 and revolving scroll 14 are provided.
The fixed scroll 10 comprises end plate 11 and spiral lap 12 disposed on surface 11a of the plate 11, and the surface facing end plate 15 which is explained later. The end plate 11 is fastened to cup-like main body 2 via bolt 13.
The revolving scroll 14 comprises end plate 15 and spiral lap 16 which is disposed on surface 15a of the plate 15, and the surface facing the end plate 11. This spiral lap 16 has substantially the same shape as spiral lap 12 included in fixed scroll 10. The axes of the revolving and fixed scrolls 14 and 10 are separated from each other by a predetermined distance, that is, they are in an eccentric relationship. In addition, the phases of these scrolls differ by 180.degree., and they are engaged with each other as shown in FIG. 3.
Accordingly, tip seals 17, provided and buried at each head surface of spiral lap 12, are in close contact with surface 15a of end plate 15, while tip seals 18, provided and buried at each head surface of spiral lap 16, are in close contact with surface 11a of end plate 11. As shown in FIG. 4, the side faces of spiral laps 12 and 16 have line contact at plural positions a, b, c, d and thus plural compression chambers 19a and 19b are formed essentially at positions of point symmetry with respect to the center of the spiral.
Inside projecting disk-shaped boss 20, provided at a center area in the outer surface (opposite to inner surface 15a) of end plate 15, drive bush 21 is inserted in a freely rotatable form via revolving bearing 23. Slide hole 24 is provided in the drive bush 21, and eccentric drive pin 25 is inserted into the slide hole 24 so as to perform a freely-sliding motion of the pin. The projecting drive pin 25 is eccentrically provided on an end face of larger-diameter portion 7a of main shaft 7, the portion 7a being provided on an end at the main body 2 side of the rotational shaft 7.
Reference numeral 26 indicates a rotation-blocking mechanism which also functions as a thrust bearing, the mechanism being provided between the peripheral edge of the outer surface of end plate 15 and an inner surface of front end plate 4. Reference numeral 27 indicates a balance weight attached to drive bush 21, reference numeral 28 indicates a suction chamber, reference numeral 29 indicates a discharge port provided by boring a central part of end plate 11 of the fixed scroll, reference numeral 30 indicates a discharge valve, reference numeral 31 indicates a discharge cavity, and reference numeral 32 indicates a balance weight attached to the larger-diameter portion 7a of main shaft 7. Reference numeral 35 indicates a retainer for restricting the rising motion of discharge valve 30, reference numeral 36 indicates a bolt for fastening the discharge valve 30 and the retainer 35 to end plate 11, and reference numeral 38 indicates a control valve.
According to the above structure, when the main shaft 7 is rotated, revolving scroll 14 is driven via eccentric drive pin 25, drive bush 21, revolving bearing 23, and boss 20, and the revolving scroll 14 revolves while rotation of the scroll 14 is prohibited by the rotation-blocking mechanism 26.
In this way, the above-mentioned line-contact portions a to d in the side faces of spiral laps 12 and 16 gradually move toward the center of the "swirl", and thereby compression chambers 19a and 19b also move toward the center of the swirl while the volume of each chamber is gradually reduced.
Accordingly, gas, which has flowed into suction chamber 28 through an inlet (not shown), enters from an opening which is limited by outer peripheral edges of spiral laps 12 and 16 into compression chambers 19a and 19b. This gas is gradually compressed and reaches central chamber 22. From the central chamber, the gas passes through discharge port 29, and presses and opens discharge valve 30, and thereby the gas is discharged into discharge cavity 31. The gas is then discharged outside via an outlet not shown.
As shown in FIG. 4, in the end plate 11 of fixed scroll 10, a pair of cylinders 32a and 32b are provided, an end of each cylinder being opened to suction chamber 28 and these cylinders being provided at both sides of discharge port 29 in a parallel form and with a specific distance between them.
Additionally, in the end plate 11, bypassing holes 33a and 33b are provided for bypassing the gas during compression from the pair of compression chambers 19a and 19b to the above cylinders 32a and 32b, and bypassing paths 44a and 44b are also provided for making the gas successively pass through the discharge port 29 and the cylinders 32a and 32b.
As shown in FIG. 5, control pressure chamber 37b is limited in cylinder 32b by closely inserting piston 34b for opening or closing the bypassing hole 33b and the bypassing path 44b into the cylinder 32b. Here, piston 34b can freely slide in the cylinder 32b.
In the piston 34b, hole 46b for opening/closing the bypassing hole 33b and hole 47b for opening/closing the bypassing path 44b are provided.
In blind opening 45 provided in piston 34b, coil spring 41b is arranged, one end thereof being disposed on the bottom of the blind opening 45b, while the other end is supported by spring bearing 40b.
At the time of a full-loading operation of the compressor, a high-pressure gas for control, generated via control valve 38, is introduced via through hole 39b into control pressure chamber 37b. Accordingly, the piston 34b proceeds against the impact-resilience force of coil spring 41b so that the piston 34b is positioned as shown in FIG. 5 and the bypassing hole 33b and bypassing path 44b are closed.
On the other hand, when in an operation mode with a controlled (or reduced) capacity, the pressure of the control gas generated via the control valve 38 is gradually lowered. Accordingly, the piston 34b receives impact-resilience force of coil spring 41b and moves backward. When hole 46b aligns with bypassing hole 33b, the gas subjected to the compression flows through bypassing hole 33b, and further passes through hole 46b, blind opening 45b, and cylinder 32b and is injected into suction chamber 28.
If the pressure of the control gas generated via the control valve 38 is further lowered, the positions of hole 47b and bypassing path 44b align with each other. Accordingly, the gas from discharge port 29 is introduced via bypassing path 44b, hole 47b, blind opening 45b, and cylinder 32b into suction chamber 28, and the capacity of the compressor becomes zero.
The structure and operation of cylinder 32a are generally the same as those of the cylinder 32b.
In the above-explained scroll-type compressor, when piston 34b slides in cylinder 32b, coil spring 41b extends or shrinks, and simultaneously rotates. Therefore, the outer-peripheral portions of the coil spring 41b are in contact with the inner-peripheral surface of the blind opening 45b, and the contact areas are subjected to abrasion.